#include <stdio.h>
#include <iostream>
using namespace std;

//Program address:  http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemId=629

//#define INPUTNUM 3

int CountTriangleNum(int sideLength);

int main()
{
	//for (int i = 0; i < INPUTNUM; ++ i)
	//{
	//	int num;
	//	cout<< "input your num:"<<endl;
	//	cin>>num;
	//	int sum = CountTriangleNum(num);
	//	cout<<sum<<endl;
	//}
	//int num1,num2,num3;
//	cin>>num1;
//	cin>>num2;
//	cin>>num3;
//	int sum1 = CountTriangleNum(num1);
//	int sum2 = CountTriangleNum(num2);
//	int sum3 = CountTriangleNum(num3);
//	cout<<sum1<<endl;
//	cout<<sum2<<endl;
//	cout<<sum3<<endl;	
//	system("pause");
      int num;
      while(cin>>num)
        {   
          if (num == EOF)
          {
            break;
          }
          
          int sum =  CountTriangleNum(num);
          cout<<sum<<endl;
        }    
	return 0;
}

int CountTriangleNum(int sideLength)
{
	int n = sideLength;
	int sum = 0;
	if (n > 1)
	{
		//sum = 	(CountTriangleNum(n - 1) + (((n + 1) * n) >> 1) + (((n - 1) * (1 + (n >> 1)) * (n >> 1)) >> 1));
		//sum = CountTriangleNum(n - 1) + n * (n + 1)/2 + (n + 1) * (n/2) - (1 + n / 2) * (n / 2);
		//if (n%2 == 1)
		//{
		//	sum = CountTriangleNum(n - 1) + n * (n + 1)/2 + (1 + n/2)*(n/2);
		//}
		//else
		//{
		//	sum = CountTriangleNum(n - 1) + n * (n + 1)/2 + (1 + n/2)*(n/2) - n/2;
		//}
		//sum = CountTriangleNum(n - 1) + (1 + n) * n / 2 + (n + 1) * (((1 + n / 2) * (n / 2)) / 2) - ((n / 2) * (n / 2 + 1) * (n + 1) / 6);
	    sum = CountTriangleNum(n - 1) + ((n * (n + 1))>>1) + (n + 1) * (n>>1) - (1 + (n>>1)) * (n>>1);
    }
	else
	{
		return 1;
	}
	return sum;
}